Restore request descriptions fallback to json-rest-spec (#2628)

Author: swallez

compiler/src/steps/add-description.ts

@@ -54,6 +54,10 @@ export default async function addDescription (model: model.Model, jsonSpec: Map<
       }
     }
 
+    if (spec.documentation.description != null) {
+      requestDefinition.description = requestDefinition.description ?? spec.documentation.description
+    }
+
     // An API endpoint is defined by an endpoint object (paths and http methods) and a request
     // type (parameters and structure).
     endpoint.description = requestDefinition.description ?? spec.documentation.description